The United States Navy in the Cold War Era: What ifs.

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This remote mount can be fitted with a Mark 19 AGL, a .50-caliber M-2, a 5.56mm M-249 SAW or other automatic weapons. The first two EX-45 mounts provided to the fleet (fitted with .50-caliber machine guns) were installed in the high-speed vessel SWIFT (HSV-2) and a Coast Guard cutter.

Developed by the Office of Naval Research, this mount is a three-axis, gyro-stabilized weapon mount coupled with a laser rangefinder and closed-circuit television. It can be fitted in ships and land vehicles, as well as in small combat craft, including the Marine Corps Small Unit Riverine Craft (SURC).

Afloat testing was conducted in 2004.

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The U.S. Army, Navy, and the Defense Advanced Research Projects Agency (DARPA) have ongoing EMG or rail gun programs. The Fiscal Year 2004 defense authorization required that the Secretary of Defense establish a collaborative program among those organizations for the evaluation and demonstration of EMG technologies and concepts.

The Navy’s program is currently oriented toward providing a long-range EMG as a fire support weapon. It will be possible to install the weapon in the planned DD(X) and CG(X) programs due to these ships are planned to have electric-drive propulsion.

The propelling charge of the EMG has an electrical energy output from 60 to 300 megajoules (MJ), and the projectile acceleration rate is 30,000-45,000Gs. In contrast, the current 5in/54-caliber gun has a muzzle energy of 10MJ and with a rocket-assisted projectile increases this to about 18MJ; the planned 6.1in AGS will have a muzzle velocity in access of 33MJ. The EMG would require a power supply of 15-30 megawatts, and approximately 6 gallons (22.7 liters) of the ship’s fuel would be required to fire each round.
In operational use, the EMG would fire in bursts of ten rounds, using command-guided projectiles or conventional ammunition.

The EMG would fire an inert round, which would use kinetic energy to damage its target. A multiple warhead is possible. The round would have no propellant, as it will be propelled entirely by the electromagnetic process. GPS guidance is projected.

The EMG is also being considered for a shipboard terminal self-defense system against attacking cruise missiles.

There is little publicly available, but these are accepted estimates:
Muzzle Velocity: Mach 6+ Rate of fire: 6-12 rounds per minute Maximum Range: 200+nm

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This weapon was a proposal for the DD 21 land-attack destroyers. Twin 6.1-inch (155mm guns) with a range of about 100nm (185km) and their magazines were to be fitted in a modular mounting that could replace Vertical Launching System (VLS) missile modules.

The gun system was to be fully automated with 1,400 rounds per module (i.e., for two guns). Projectiles up to 6 ½ ft (1.9m) long and weighing 300lbs (136kg) could be handled by VGAS. The sustained rate of fire was to be 15 rounds per minute, per barrel.

In any event, the Navy made the decision not to pursue the development of VGAS.